xxxii Chemical Section. [December i8th } 1919. 



liquid fuels the lighter petroleum products were almost waste 

 products, and were used for heating stills, boilers, etc., and in 

 some cases were even allowed to evaporate away. The actual 

 separation of these volatile products was necessary on account 

 of the flash point regulations dealing with the storage, and 

 transport of the heavier petroleum products. 



The demand for petrol for automobile engines was therefore 

 readily met in the early da}'S of the petrol engine, though it 

 was necessary to subject the volatile products to the acid and 

 alkali washes known as the refining process. The specific 

 gravity of motor spirit in 1905 was about .690 at 15 C, and it 

 was a highly volatile product. To-day some grades of "spirit" 

 have specific gravities as high as .760. 



The import of petrol into this country in 1905 was 18,000,000 

 gallons, and in 1914, 120,000,000 gallons. The increased demand 

 has been met in the first place by extending the limits of the 

 M cut " for the petrol fractions to include higher boiling frac- 

 tions. As this produced heavier spirit, and the engines of that 

 day were only capable of utilising highly volatile fractions, 

 the demand would have exceeded the supply if the invention of 

 the jet carburettor had not saved the situation by allowing the 

 use of heavier spirit, and of spirit collected over wider ranges of 

 temperature. Following this development the temperature 

 ranges of the " cut " in the distillation were increased to 

 include both heavier and lighter products, and of recent years 

 the heavier constituents of natural gas have been condensed by 

 pressure and cooling and used as a " livening " agent. 



These developments would have been insufficient to cope with 

 the increasing demand for spirit had it not been for the intro- 

 duction of cracking on a large scale. Cracking consists of 

 subjecting heavy petroleum oils (usually of higher boiling 

 point than kerosene) to heat and pressure, wmereby compounds 

 of lower molecular weight, and therefore lower boiling point 

 are produced. Cracked spirit is of higher gravity than 

 " straight " distilled spirit of the same boiling point. It is 

 slightly disagreeable as regards smell, but otherwise a good 

 fuel. Nearly all of the cracked spirit produced in the United 

 States is taken up by the home market, the straight distilled 

 spirit being exported. This process increases the possible yield 

 of spirit from an average of 5 to 10% on the crude oil to 50 to 

 80% of the crude oil, which alters the entire aspect of the motor 

 spirit problem. 



In the present position there is little fear of a motor spirit 

 shortage until there is a shortage of all petroleum products. 

 The question now resolves itself into one of which product can 

 stand the highest price. Probably lubricating oils and medicinal 



